Optimal Biodegradable Scaffolds and Progenitor Cells for Effective Bone Regenerat

描述(由申请人提供)：骨修复和再生是一个不断扩大的、价值数十亿美元的市场，通过口腔/颌面和矫形外科领域得到满足。常见的病例包括创伤导致的骨丢失、肿瘤切除、翻修手术、发育畸形和骨不连骨折，以及因牙齿缺失和牙周病而导致的牙骨丢失。目前可用的治疗方案(如自体移植、同种异体移植等)远不理想，往往导致有限程度的结构和功能恢复，以及其他严重并发症。骨组织工程(BTE)可能是一种更好的替代治疗方法。成功的BTE关键依赖于有效的三维、可生物降解的支架和充足的血管供应。这项研究的总体目标是开发一种优化的可生物降解支架，种植临床相关细胞以促进增强的骨再生和血管形成。由于聚(85-丙交酯-15-乙交酯)(PLGA)微球支架具有生物可降解性、骨相容性和与人骨的力学相容性，因此本研究主要针对其进行研究。不幸的是，这些微球支架(孔径约100 5m)实现的骨再生仅限于支架表面，这是因为无法支持足够的氧气和营养物质的传输，以及新生血管的形成。具有更大孔径的非PLGA微球支架(例如，&gt；400 5m)，尽管在机械上与人骨再生不兼容，但已被证明可以缓解这些限制，改善细胞渗透，最终允许增加整个支架的骨形成和血管形成。此外，最近的研究表明，体外血管形成前支架通过与两个临床相关的细胞群体--外周血来源内皮祖细胞(EPC)和骨髓来源间充质干细胞(MSCs)共同培养，在体内促进骨形成和血管形成。我们假设，预血管化的、机械强度较高的PLGA微球支架具有更大的孔径(即中等大小的毛孔)，通过改善整个支架的细胞增殖、矿化和血管化，将促进更多的骨形成。我们建议通过三步走的过程来实现这一主要目标。首先，我们将设计、制造和表征(即孔隙率、互连性和机械强度)新型中孔和机械强度的PLGA微球支架。其次，我们将评估这些中等孔隙率的PLGA微球支架与对照支架相比，在体外显示增强矿化和形成原始血管网络的能力。最后，我们将通过兔尺骨骨缺损模型，研究我们的预血管化的中孔PLGA微球支架在体内增强骨再生的能力。我们的方法旨在通过开发一种能够实现全功能和结构性骨再生的技术，显著促进基于支架的骨移植的最先进水平。

DESCRIPTION (provided by applicant): Bone repair and regeneration represents an expanding, multi-billion dollar market addressed through the fields of oral/maxillofacial and orthopaedic surgery. Common cases involve bone loss due to trauma, tumor resection, revision surgery, developmental deformities and non-union fractures, and dental bone loss as a result of missing teeth and periodontal disease. Currently available treatment options (i.e., autografts, allografts, etc.) are far from ideal, often resulting in a limited degree of structural and functional recovery, as well as other serious complications. Bone tissue engineering (BTE) may serve as a superior alternative treatment. Successful BTE critically depends on an effective three-dimensional, biodegradable scaffold, and an adequate vascular supply. The overall objective of this study is to develop an optimized biodegradable scaffold, seeded with clinically relevant cells to promote enhanced bone regeneration and vascularization. This study focuses on poly(85 lactide-co-15 glycolide) (PLGA) microsphere scaffolds since they are biodegradable, osteocompatible, and mechanically compatible with human bone. Unfortunately, bone regeneration achieved with these microsphere scaffolds (pore size ~100 5m) is limited to the scaffold surfaces, due to failure to support sufficient mass transport of oxygen and nutrients, and neo-vascularization. Non-PLGA microsphere scaffolds with larger pore sizes (i.e., > 400 5m), although not mechanically compatible with human bone regeneration, have been shown to ease these limitations, improve cell infiltration, and ultimately, allow for increased bone formation and vascularization throughout the entire scaffold. In addition, recent work has demonstrated that pre-vascularizing scaffolds in vitro by co-culturing two clinically relevant cell populations, peripheral blood derived - endothelial progenitor cells (EPCs) and bone marrow derived - mesenchymal stem cells (MSCs), enhances both bone formation and vascularization in vivo. We hypothesize that pre-vascularized, mechanically strong PLGA microsphere scaffolds with increased pore size (i.e., moderately-sized pores) will promote increased bone formation, by improving cell proliferation, mineralization and vascularization throughout the entire scaffold. We propose to achieve this main objective through a three- step process. First, we will design, fabricate and characterize (i.e., porosity, interconnectivity and mechanical strength) novel moderately-porous and mechanically strong PLGA microsphere scaffolds. Second, we will assess the ability of these moderately-porous PLGA microsphere scaffolds seeded with two clinically-relevant cell populations to demonstrate enhanced mineralization and the formation of primitive vascular networks compared to control scaffolds in vitro. Lastly, we will study the enhanced bone regeneration ability of our pre- vascularized moderately-porous PLGA microsphere scaffolds in vivo via a rabbit ulnar bone defect model. Our approach is designed to significantly advance the state-of-the-art in scaffold-based BTE through the development of a technique to enable fully functional and structural bone regeneration.